Skip to contents

Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.

Setup code

To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:

library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)

plotly_widget <- plot_ly(x = diamonds$cut) %>%
  config(displayModeBar = FALSE) %>%
  layout(margin = list(t = 0, b = 0, l = 0, r = 0))

leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
  leaflet(options = .) %>%
  addTiles()

Shiny usage

Cards work equally well in Shiny. In the examples below, replace plotly_widget with plotlyOutput() and leaflet_widget with leafletOutput() to adapt them for Shiny server-rendered plots/maps.

Hello card()

A card() is designed to handle any number of “known” card items (e.g., card_header(), card_body(), etc) as unnamed arguments (i.e., children). As we’ll see shortly, card() also has some useful named arguments (e.g., full_screen, height, etc).

At their core, card() and card items are just an HTML div() with a special Bootstrap class, so you can use Bootstrap’s utility classes to customize things like colors, text, borders, etc.

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  card_body(
    markdown("Some text with a [link](https://github.com)")
  )
)
A header

Some text with a link

Implicit card_body()

If you find yourself using card_body() without changing any of its defaults, consider dropping it altogether since any direct children of card() that aren’t “known” card() items, are wrapped together into an implicit card_body() call.1 For example, the code to the right generates HTML that is identical to the previous example:

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  markdown("Some text with a [link](https://github.com).")
)
A header

Some text with a link.

Restricting growth

By default, a card()’s size grows to accommodate the size of its contents. Thus, if a card_body() contains a large amount of text, tables, etc., you may want to specify a height or max_height. That said, when laying out multiple cards, it’s likely best not to specify height on the card(), and instead, let the layout determine the height layout_column_wrap().

Although scrolling is convenient for reducing the amount of space required to park lots of content, it can also be a nuisance to the user. To help reduce the need for scrolling, consider pairing scrolling with full_screen = TRUE (which adds an icon to expand the card’s size to the browser window). Notice how, when the card is expanded to full-screen, max_height/height won’t effect the full-screen size of the card.

card(
  max_height = 250,
  full_screen = TRUE,
  card_header(
    "A long, scrolling, description"
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A long, scrolling, description

Ipsum proin lacus, venenatis condimentum facilisi montes integer, eleifend dis erat. Vehicula tortor penatibus non suscipit purus; fames accumsan magnis, quis montes taciti potenti. Phasellus aliquet sociis lectus facilisis sagittis fusce massa quam, quam tincidunt auctor. Morbi platea vel molestie sagittis libero inceptos ultrices, porta quis neque? Pretium massa mattis curabitur quisque duis nunc.

Adipiscing netus leo morbi suscipit orci in cursus. Lobortis odio cursus netus dis a volutpat montes fermentum posuere, curae enim. Mi aptent conubia ultrices elementum, ligula malesuada consequat? Himenaeos nisl commodo sociosqu, accumsan nec bibendum risus fames torquent? Faucibus senectus ante luctus turpis ultrices interdum elementum praesent vehicula cubilia.

Adipiscing mus lacinia ullamcorper molestie mattis id. Blandit duis class, porta imperdiet velit himenaeos faucibus. Parturient felis vestibulum luctus nunc, diam mus – fames class potenti commodo? Suspendisse senectus metus aliquam per dignissim lectus ultrices nam mi. Ornare in nascetur nibh, nunc feugiat venenatis, maecenas suspendisse, sem volutpat enim, dictumst fames lobortis non facilisi ridiculus?

Filling outputs

A card()’s default behavior is optimized for facilitating filling layouts. More specifically, if a fill item (e.g., plotly_widget), appears as a direct child of a card_body(), it resizes to fit the card()s specified height. This means, by specifying height = 250 we’ve effectively shrunk the plot’s height from its default of 400 down to about 200 pixels. And, when expanded to full_screen, the plot grows to match the card()’s new size.

card(
  height = 250,
  full_screen = TRUE,
  card_header("A filling plot"),
  card_body(plotly_widget)
)
A filling plot

Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny output bindings (e.g, plotOutput(), imageOutput(), etc) are fill items by default, so this behavior “just works” in those scenarios. And, in some of these situations, it’s helpful to remove card_body()’s padding, which can be done via spacing & alignment utility classes.

card(
  height = 275,
  full_screen = TRUE,
  card_header("A filling map"),
  card_body(
    class = "p-0",
    leaflet_widget
  ),
  card_footer(
    class = "fs-6",
    "Copyright 2023 RStudio, PBC"
  )
)
A filling map

Fill item(s) aren’t limited in how much they grow and shrink, which can be problematic when a card becomes very small. To work around this, consider adding a min_height on the card_body() container. For example, try using the handle on the lower-right portion of this card example to make the card taller/smaller.

This interactive example is a bit contrived in that we’re using CSS resize to demonstrate how to make plots that don’t shrink beyond a certain point, but this concept becomes quite useful when implementing page-level filling layouts (i.e., page_fillable()) with multiple cards.

card(
  height = 300,
  style = "resize:vertical;",
  card_header("Plots that grow but don't shrink"),
  card_body(
    min_height = 250,
    plotly_widget,
    plotly_widget
  )
)
Plots that grow but don't shrink

Troubleshooting fill

As you’ll learn more about in filling layouts, a fill item loses its ability to fill when wrapped in additional UI element that isn’t a fillable container. To fix the situation, use as_fill_carrier() to allow the additional element to carry the potential to fill from the card_body() down to the fill item.

Multiple card_body()

A card() can have multiple card_body()s, which is especially useful for:

  1. Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
  2. Allowing each card_body() to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g., min_height).

For example, when pairing filling output with scrolling content, you may want min_height on the filling output since the scrolling content will force it to shrink:

card(
  height = 375,
  full_screen = TRUE,
  card_header(
    "Filling plot, scrolling description"
  ),
  card_body(
    min_height = 200,
    plotly_widget
  ),
  card_body(
    class = "lead container",
    lorem::ipsum(paragraphs = 10, sentences = 5)
  )
)
Filling plot, scrolling description

Ipsum sodales euismod rhoncus posuere diam nibh vulputate mi – imperdiet metus? Gravida himenaeos magna maecenas feugiat nascetur praesent, tempor molestie. Nunc convallis cras iaculis sapien metus lacus id est. Nascetur dictumst proin praesent massa aliquet nisi laoreet phasellus. Odio varius hac rutrum facilisi senectus aliquet venenatis dapibus fusce felis – felis a lobortis parturient, feugiat congue mauris sodales convallis fames venenatis rhoncus.

Sit parturient varius faucibus sodales semper ligula primis, taciti porta? Feugiat dignissim sed platea risus mollis egestas suspendisse magnis. Eget vivamus laoreet primis leo iaculis vehicula est dis eros mus. Mauris cursus curabitur mauris ornare, metus congue auctor? Aenean praesent curae eu nostra mattis ridiculus dapibus at cras porttitor enim mollis, ornare dictumst!

Consectetur per arcu sollicitudin, viverra ante tellus habitant odio fames! Metus class, nulla conubia orci ullamcorper ornare – condimentum curae primis odio sed. Facilisis dapibus maecenas rhoncus sagittis orci nec elementum, fermentum massa dis faucibus. Fames mi potenti tortor, nascetur lobortis cursus non tristique ante. Tristique habitasse sollicitudin sodales justo – magna semper potenti.

Adipiscing sem suscipit molestie rhoncus sociosqu, dui in lacinia maecenas egestas faucibus dignissim orci litora. Ac molestie libero feugiat euismod potenti, conubia proin quam elementum! Habitasse metus tempor eu augue molestie facilisi morbi nam vitae. Sociosqu ultrices cursus – per convallis ante accumsan id mi? Est neque praesent egestas sem gravida feugiat?

Elit urna tristique cursus dictumst magna risus pharetra pretium? Tempor elementum sociosqu libero – posuere senectus faucibus! Habitant turpis quam magna, habitasse pellentesque felis cursus – ad litora euismod mattis sed. Est mattis ornare ornare rutrum, in conubia class! Congue ut sagittis magna, fringilla facilisis habitant pretium nisl habitant.

Ipsum sociis risus ridiculus: urna, erat gravida vel dapibus feugiat nascetur? Dictumst vitae, facilisis leo sem: nibh pretium et! Diam himenaeos condimentum, urna velit interdum suspendisse donec bibendum. Sollicitudin interdum sed aliquet dictum, tortor varius eget sapien. Aliquet morbi laoreet tellus euismod eu tellus feugiat magnis eleifend eu nascetur placerat augue enim risus posuere libero porttitor aenean.

Adipiscing lacinia potenti sagittis – commodo metus aliquam montes commodo enim maecenas. Varius semper non sodales aenean penatibus placerat pellentesque. Curae hac rutrum feugiat tempus hendrerit primis mi, primis dictum aliquet. Netus dictum sapien eros, odio sapien, suspendisse aliquet mi imperdiet. Nulla vestibulum purus vehicula, dignissim dictum dignissim.

Elit placerat potenti ultrices, ornare venenatis luctus – mus eleifend volutpat velit nullam: interdum praesent cubilia mollis dictum! Feugiat habitant nam eros penatibus taciti hendrerit sollicitudin, dictum sociis integer! Molestie nisi tincidunt inceptos eleifend sagittis imperdiet magna sed! Cum per sodales; cursus libero quisque, parturient, tincidunt imperdiet fermentum. Id cum tempor.

Elit montes venenatis ut viverra lacinia nisi malesuada; commodo eu vitae maecenas nibh! Porta tincidunt pretium fringilla, class morbi ad ullamcorper donec eu ridiculus nullam nec? Cum iaculis aenean nibh etiam nisi senectus, hendrerit, primis lacinia magnis cras. Fermentum pellentesque ante, himenaeos inceptos consequat in taciti vulputate sollicitudin! Cursus lectus augue.

Lorem eget aptent facilisis sapien, aenean a cum aliquam tincidunt. Vehicula bibendum aliquam – aptent cras tincidunt sociosqu dictum volutpat a ut inceptos. Tristique maecenas tortor sapien erat faucibus lobortis. Erat orci enim porta quisque cubilia euismod auctor ac nam pulvinar aliquet hac. Feugiat litora augue tempor aenean venenatis in eros commodo!

Also, when the content has a fixed size, and should not be allowed to scroll, set fill = FALSE:

card(
  height = 350,
  full_screen = TRUE,
  card_header(
    "Filling plot, short description"
  ),
  plotly_widget,
  card_body(
    fill = FALSE, gap = 0,
    card_title("A subtitle"),
    p(class = "text-muted", "And a caption")
  )
)
Filling plot, short description
A subtitle

And a caption

Multiple columns

As you’ll learn in column-based layouts, layout_column_wrap() is great for multi-column layouts that are responsive and accommodate for filling output. Here we have an equal-width 2-column layout using width = 1/2, but it’s also possible to have varying column widths.

card(
  height = 350,
  full_screen = TRUE,
  card_header("A multi-column filling layout"),
  card_body(
    min_height = 200,
    layout_column_wrap(
      width = 1/2,
      plotOutput("p1"),
      plotOutput("p2")
    )
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A multi-column filling layout

Amet dictum fringilla magnis fames lectus nisi, arcu etiam sem semper! Imperdiet lacinia et mauris, blandit sociosqu turpis turpis? Vehicula sed vestibulum auctor libero – ut venenatis quis tempus class fringilla. Congue magna venenatis facilisi taciti eget. Posuere ridiculus pretium eros, sem dis nunc accumsan suscipit lacinia.

Amet facilisi, vivamus parturient sapien justo aliquet. Dictumst lectus mollis, sodales, aliquam lacus justo feugiat, sapien torquent. Ante habitasse aptent – placerat urna neque tellus ad in? Viverra vel molestie aptent risus ridiculus integer fusce facilisi, malesuada elementum varius. Imperdiet semper condimentum integer, parturient tempor ad sapien id!

Consectetur venenatis ante bibendum quam, suspendisse pharetra nec ad, iaculis lacinia nec! A auctor nullam varius posuere velit eleifend. Nullam id maecenas sapien – parturient, nascetur dignissim netus! Lobortis fringilla hendrerit, euismod felis: nullam, metus cum aptent. Varius torquent duis, ad ultricies!

Multiple cards

layout_column_wrap() is especially nice for laying out multiple cards since each card in a particular row will have the same height (by default). Learn more in column-based layouts.

layout_column_wrap(
  width = 1/2,
  height = 300,
  card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
  card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)
A filling plot
A filling map

Multiple tabs

navset_card_tab() and navset_card_pill() make it possible to create cards with multiple tabs or pills. These functions have the same full_screen capabilities as normal card()s as well some other options like title (since there is no natural place for a card_header() to be used). Note that, each nav_panel() object is similar to a card(). That is, if the direct children aren’t already card items (e.g., card_title()), they get implicitly wrapped in a card_body().

library(leaflet)
navset_card_tab(
  height = 450,
  full_screen = TRUE,
  title = "HTML Widgets",
  nav_panel(
    "Plotly",
    card_title("A plotly plot"),
    plotly_widget
  ),
  nav_panel(
    "Leaflet",
    card_title("A leaflet plot"),
    leaflet_widget
  ),
  nav_panel(
    shiny::icon("circle-info"),
    markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
  )
)
HTML Widgets
A plotly plot
A leaflet plot

Learn more about htmlwidgets

As you’ll learn more about in sidebar layouts, layout_sidebar() just works when placed inside in a card(). In this case, if you want fill items (e.g., plotly_widget) to still fill the card like we’ve seen before, you’ll need to set fillable = TRUE in layout_sidebar().

card(
  height = 300,
  full_screen = TRUE,
  card_header("A sidebar layout inside a card"),
  layout_sidebar(
    fillable = TRUE,
    sidebar = sidebar(
      actionButton("btn", "A button")
    ),
    plotly_widget
  )
)
A sidebar layout inside a card

Static images

card_image() makes it easy to embed static (i.e., pre-generated) images into a card. Provide a URL to href to make it clickable. In the case of multiple card_image()s, consider laying them out in multiple cards with layout_column_wrap() to produce a grid of clickable thumbnails.

card(
  height = 300,
  full_screen = TRUE,
  card_image(
    file = "shiny-hex.svg",
    href = "https://github.com/rstudio/shiny"
  ),
  card_body(
    fill = FALSE,
    card_title("Shiny for R"),
    p(
      class = "fw-light text-muted",
      "Brought to you by RStudio."
    )
  )
)
Shiny for R

Brought to you by RStudio.

Flexbox

Both card() and card_body() default to fillable = TRUE (that is, they are CSS flexbox containers), which works wonders for facilitating filling outputs, but it also leads to surprising behavior with inline tags (e.g., actionButton(), span(), strings, etc). Specifically, each inline tag is placed on a new line, but in a “normal” layout flow (fillable = FALSE), inline tags render inline.

card(
  card_body(
    fillable = TRUE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn1", "A button")
  ),
  card_body(
    fillable = FALSE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn2", "A button")
  )
)
Here's some inline text
Here's some inline text

That said, sometimes working in a flexbox layout is quite useful, even when working with inline tags. Here we leverage flexbox’s gap property to control the spacing between a plot, a (full-width) button, and paragraph. Note that, by using markdown() for the paragraph, it wraps the results in a <p> tag, which means the contents of the paragraph are not longer subject to flexbox layout. If we wanted, we could do something similar to render the actionButton() inline by wrapping it in a div().

card(
  height = 325, full_screen = TRUE,
  card_header("A plot with an action links"),
  card_body(
    class = "gap-2 container",
    plotly_widget,
    actionButton(
      "go_btn", "Action button",
      class = "btn-primary rounded-0"
    ),
    markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
  )
)
A plot with an action links

Here's a simple hyperlink.

In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.

card(
  height = 300, full_screen = TRUE,
  card_header(
    class = "d-flex justify-content-between",
    "Centered plot",
    checkboxInput("check", " Check me", TRUE)
  ),
  card_body(
    class = "align-items-center",
    plotOutput("id", width = "75%")
  )
)
Centered plot

Shiny

Since this article is statically rendered, the examples here use statically rendered content/widgets, but the same card() functionality works for dynamically rendered content via Shiny (e.g., plotOutput(), plotlyOutput(), etc).

An additional benefit that comes with using shiny is the ability to use getCurrentOutputInfo() to render new/different content when the output container becomes large enough, which is particularly useful with card(full_screen = T, ...). For example, you may want additional captions/labels when a plot is large, additional controls on a table, etc (see the value boxes article for a clever use of this).

# UI logic
ui <- page_fluid(
  card(
    max_height = 200,
    full_screen = TRUE,
    card_header("A dynamically rendered plot"),
    plotOutput("plot_id")
  )
)

# Server logic
server <- function(input, output, session) {
  output$plot_id <- renderPlot({
    info <- getCurrentOutputInfo()
    if (info$height() > 600) {
      # code for "large" plot
    } else {
      # code for "small" plot
    }
  })
}

shinyApp(ui, server)

Appendix

The following CSS is used to give plotOutput() a background color; it’s necessary here because this documentation page is not actually hooked up to a Shiny app, so we can’t show a real plot.

.shiny-plot-output {
  background-color: #216B7288;
  height: 400px;
  width: 100%;
}